Title: Chemically Accurate Prediction of CO2 Adsorption Thermodynamics in Metal–Organic Framework CALF-20: Complementary Ab Initio Modeling and Grand Canonical Monte Carlo Simulations
Authors: Kaido Sillar, Sonja Grubišić, Ivana S. Đorđević, Majdi Hochlaf
Date: 2026-02-02
Working Group: WG2
Grant Period: GP2
Grant Period Goal (number): GPG4; GPG5
Covered deliverables from the MoU (number): 2. 1. 1.; 2. 2. 1.
Countries involved: Serbia, Estonia, France
Number of female/young/ITC coauthors: 2/1/3
Is the publication open access?: Yes
Is the publication co-lead by a YRI?: No
Abstract: Carbon dioxide adsorption thermodynamics in the metal–organic framework CALF-20, a hydrothermally stable candidate for carbon capture, are predicted using two complementary approaches. An analytical ab initio thermodynamics method combines periodic density functional theory + dispersion interactions (DFT + D) with MP2 corrections for adsorption energies, local sampling of the potential energy surface, and a nonisolated-site term to capture nonlocal effects. Grand Canonical Monte Carlo(GCMC) simulations using a newly developed force field enable comprehensive sampling of global configurations. Both methods reproduce experimental adsorption isotherms and heats of adsorption within chemical accuracy (±4 kJ mol−1). Dispersion dominates CO2 binding (>80%), while quantum effects on nuclear motion (zero-point vibrational energy) contribute up to 5.4 kJ mol−1 to adsorption thermodynamics—impacting both adsorption enthalpies and Gibbs free energies. Nonlocal effects reduce entropy penalties by ≳7 kJ mol−1, yielding adsorption Gibbs free energies that reveal a two-step pore filling mechanism: initial single occupancy of cages followed by intracage pairing. Triple cross-validation across ab initio, GCMC, and experiment confirms this cooperative two-step mechanism and reinforces the reliability of the thermodynamic dataset. This transferable strategy enables predictive modeling of adsorption thermodynamics in nanoporous materials for next-generation carbon-capture applications.
